Mixing vessels may be used in a variety of industrial applications. They may be used as precipitators in alumina production, anaerobic digesters in waste water treatment, and in many other applications.
Impellers are frequently used to mix gas into a liquid in situations where high efficiency and high power are needed. Typical industrial applications for such impellers include plastic and production of terephthalic acid, fermentation, production of antibiotics, and hydrogenation.
It is generally desirable for an impeller assembly that is used for dispersing gasses or liquids into liquids to have certain characteristics. Some advantageous characteristics include (1) a low power number (i.e., an impeller power constant that is related to the specific geometry of the impeller, which is related to the ratio of the mechanical drive power draw to the radial pumping energy transmitted to the fluid), (2) high gas disbursement capacity without flooding (i.e., when the impeller blades are inundated by a high amount of gas, such that liquid pumping is substantially diminished), (3) flat power characteristics (consistency of power draw) regardless of the rate of gas injection or disbursement into the mixing vessel (i.e., an impeller may lose power while mixing gas into a liquid), and (4) the capability to suspend solid particles in the liquid in the vessel during gas injection.
The impeller according to the present invention encompasses is generally directed to such characteristics, but the present invention is not limited to possessing all of these characteristics.